The present invention relates to a plasma processing method and apparatus and a tray for plasma processing to be utilized for manufacturing electronic devices, micro machines (MEMS: Micro Electromechanical Systems), boards for mounting components, and the like.
FIG. 19 shows one example of a generic parallel plate type plasma processing apparatus.
Referring to FIG. 19, if a vacuum chamber 201 is evacuated by a pump 203, as an exhauster, while introducing a specified gas by a gas supply unit 202 into the vacuum chamber 201 and high-frequency power of 13.56 MHz is applied to a substrate electrode 206 by a substrate electrode high-frequency power supply 210 while maintaining an interior of the vacuum chamber 201 at a specified pressure by a pressure-regulating valve 204, then plasma is generated in the vacuum chamber 201, and a substrate 209 placed on the substrate electrode 206 can be subjected to plasma processing of etching, deposition, surface reforming, or the like. Turbo-molecular pump 203 and an exhaust port 211 are disposed just under the substrate electrode 206, and the pressure-regulating valve 204 is an up-and-down valve disposed just under the substrate electrode 206 and just over the turbo-molecular pump 203. The substrate electrode 206 is fixed to the vacuum vessel 201 with four props 212. Moreover, an opposite electrode 241 is provided oppositely to the substrate electrode 206.
As another plasma processing apparatus, there is a plasma processing apparatus of a high-frequency induction system for generating plasma in a vacuum vessel by applying high-frequency power to a coil. The plasma processing apparatus of this system, which generates plasma by generating a high-frequency magnetic field in the vacuum vessel and accelerating electrons by generating an inductive electric field inside the vacuum vessel by its high-frequency magnetic field, is able to generate plasma of a density higher than parallel plate type plasma.
FIG. 20 shows one example of this construction. Referring to FIG. 20, by evacuating a vacuum chamber 201 by a turbo-molecular pump 203, as an exhauster, while introducing a specified gas from a gas supply unit 202 into the vacuum vessel 201 and by applying high-frequency power of 13.56 MHz to a coil provided along a dielectric plate 207, opposite to a substrate electrode 206, by a coil use high-frequency power supply 205 while maintaining an interior of the vacuum vessel 201 at a specified pressure by a pressure-regulating valve 204, inductive-coupling type plasma is generated in the vacuum vessel 201, and a substrate 209 placed on the substrate electrode 206 can be subjected to plasma processing.
There is also provided a substrate-electrode use high-frequency power supply 210 for supplying high-frequency power to the substrate electrode 206, thereby making it possible to control ion energy that reaches the substrate 209. The turbo-molecular pump 203 and the exhaust port 211 are disposed just under the substrate electrode 206, and the pressure-regulating valve 204 is an up-and-down valve disposed just under the substrate electrode 206 and just over the turbo-molecular pump 203. The substrate electrode 206 is fixed to the vacuum vessel 201 with four props 212.
Up to now, various materials have been used as surface material of the substrate electrode. Besides metals such as aluminum and stainless steel, there have been an example in which only a part of a surface of a substrate electrode is covered with an insulating layer (hard alumite), and only the insulating layer is brought into contact with a substrate as disclosed in U.S. Pat. No. 2,758,755, an example in which a substrate electrode portion to be brought into contact with a substrate is covered with a dielectric film (vinyl chloride, Teflon (the registered trademark of U.S. Dupont of Polytetrafluoroethylene resin mold), or polyimide) as disclosed in Japanese Laid-Open Patent Publication No. 2-155230, an example in which a substrate electrode portion to be brought into contact with a substrate is covered with a dielectric film constructed of at least one of vinyl chloride, Teflon, and polyimide, and a self-bias voltage of the substrate electrode is monitored to detect damage of the dielectric film as disclosed in U.S. Pat. No. 3,010,683, and so on. As described above, if a dielectric layer is provided between the substrate and the substrate electrode, there is an effect of reducing charge-up damage.
There is another method for improving thermal conduction of a substrate and a substrate electrode by covering a surface of the substrate electrode with a ceramic layer and applying a DC voltage to a DC electrode buried in the ceramic layer for suction of the substrate onto the substrate electrode surface with an electrostatic force, or for pressing of the substrate against the substrate electrode by a clamp ring. There is also a method for improving thermal conduction of a substrate and a substrate electrode by supplying gas (helium or the like), which becomes a thermal medium, between the substrate and the substrate electrode.
However, the aforementioned conventional system has had an issue in that, if it has been attempted to process a thin soft substrate (resin sheet, for example), a temperature of the substrate has disadvantageously been raised by plasma exposure.
This is attributed to the fact that heat exchange between the substrate and the substrate electrode becomes insufficient in a vacuum in addition to a small thermal capacity of the substrate. If it is attempted to suck the substrate onto the substrate electrode surface with an electrostatic force, then a direct current scarcely flows through a dielectric substrate, and the suction cannot take effect. Moreover, if gas that becomes a thermal medium is supplied between the substrate and the substrate electrode with the substrate pressed against the substrate electrode by a clamp ring, then the substrate is significantly deformed because the substrate is thin and soft. This not only impairs uniformity of processing but also possibly generates abnormal discharge in a space formed between the substrate and the substrate electrode, thereby lacking practicability.
Moreover, if gas that becomes a thermal medium is supplied between the substrate and the substrate electrode when the substrate is large, thin, hard, and easy to break (silicon, glass, ceramics, or the like) in the conventional system, then the substrate significantly deforms because the substrate is thin, and the substrate sometimes breaks. Particularly, when a substrate thickness is not greater than 1 mm and an area is not smaller than 0.1 m2, the aforementioned issue sometimes occurs.